Essex Hot Air Engine

[Dave Otto]

Hi Everyone
Next on the list to be worked on is the flywheel


Here is the untouched casting, I wasn’t completely thrilled with it but it is just a casting after all. I was kicking around carving one from a solid piece of cast iron but decided to go ahead and see what I could do with it.


After some fettling and a trip through the blast cabinet it is starting to look better.


I used my large 8” 3 jaw chuck to grip the inside rim. This is an adjust-tru type so I was able to use that feature get the inner rim running as true as possible.


The outside was a different story, so I decided to re-profile the outer hemisphere. Using the step and cut method the rim is trued up; here you can lines of red Dykem that show there is still some filing that needs to be done.


Once the first side was done the flywheel was flipped around and the process repeated.
A form tool was ground from HSS to cut the belt groove down the center. The same tool will be used to machine the belt grooves in the crank.


Next the hubs are brought to length and the bore for the crank shaft is drilled and bored to size.


Moving over to the mill here is my setup to drill and ream for the flywheel crankpin. By dropping a pin into the bore the flywheel can be rotated on it’s axis to align the crankpin boss for the best fit.


After several iterations of loosen clamps rotate, re-clamp, jog over in X, check to see how you did etc. Because of the engine stroke, the X position is fixed but the idea is to get it centered rotationally at that position. You can see that I traced around the pin with a Sharpie to better see how I was doing.


The crankshaft was turned and Loctited into the flywheel. I was concerned about cracking the cast alloy trying to do a press or shrink fit, so decided that Loctite it is.


The crankpin and thrust washer were turned from 1144 steel and case hardened. The crankpin was also installed using Loctite, the washer is free floating.


Here is a shot of it on the engine frame. I’m pretty happy with how it turned out; with some high build primer and sanding I think that it will look pretty good.

Thanks for checking in.

More later,
Dave

[Dave Otto]

Hi Everyone, Here is a quick update showing some of the work on the water jacket.


Like the other castings there was quite a bit of fettling to smooth this one up especially around the parting lines and around the 3 bosses. It came out looking pretty good though.
Here the back side where it mounts to the displacer cylinder is faced off and brought to proper thickness.


The casting is flipped over and aligned with the mill’s X axis. Then the center bore is put in along with the two mounting holes. The water fill boss is also squared up and brought to proper length.


The water jacket is mounted to an angle plate and each boss is machined. The two lower ones are for the core plugs. The casting was rotated and realigned for each boss.


I decided to follow the plans and machine the core plugs from aluminum, and Loctite them in. They were turned to size on each end of a piece of stock then the Square is machined using the CNC. Makes it nice for this type of thing, you can add a small radius to the corners and chamfer the top edge all in one operation.


The plugs are parted off and ready to install. I thought about using steel threaded plugs which I had some of, but decided that it just wasn’t worth the risk possibly cracking the casting running a tapered tap into a relatively thin part. Everything gets painted anyway, so I think that these will be just fine.


Here is the water jacket temporally mounted on the engine after the core plugs have been installed.


And a view from the rear.

Thanks for stopping by.

More later,
Dave

[Kim]

Nice post Dave.  Your pictures are always so crisp and clear (not to mention swarf free! )
Kim

[Dave Otto]

Thanks Kim!
The Nikon Coolpix P530 does do a nice job.

I dropped the power cylinder off at my buddy's automotive machine shop after work today, he will do his magic with the Sunnen hone; then I will be able to fit the piston.


Dave

[Dave Otto]

Hi everyone,
Next up is work on the crank.


Starting out the crank is roughed out of a piece of 1144 stock.


After the piece had been faced to length with a chucking lug left on the rear. It was flipped around and held in a collet and supported with the live center. The same form tool is used to cut the belt grooves.


Moved over to the mill, it is set up drill and ream for the crank pin.


The crank pin was cut form a 7/32” HSS drill blank and pressed into place.


Here is a shot of the crank installed on the crankshaft.

Thanks for stopping by,
Dave

[Admiral_dk]

Beautiful work Dave, on a very different engine 

Per

[Chipmaster]

Yes excellent work and always so clean.

Andy

[Dave Otto]

Per & Andy, thanks for the comments I do appreciate them.

Dave

[Dave Otto]

Hi Everyone
Here are some photos of the Furnace Base and Burner construction.



I started out with the supplied aluminum casting, but after getting it most of the way completed I decided that I wanted something that looked more original to the engine. The engines with a town gas burner had a boss where the gas pipe screwed in. The design of the replica has it machined as a separate part.


Using a suitable piece of cast iron bar stock a start was made, the boss will have draft but at this point I left it straight so it could be used as a chucking lug.



The part was turned around and the profile turned along with the inner features. I had a 3/8”32 tap so that is what I used. The plans called for a 3/8”-40


Now it is turned around again and the casting draft is added to the boss.


Next over to the mill and the holes are added, two air holes and two mounting screw holes.


Then the 3/8”-32 hole for the burner barrel is put in.


So after thinking about it a bit I decided to remove some of the mass from the base. I plan to add some insulation in this area to help reduce the radiant heat into this part. Back into the lathe to take 1/8” out of the bottom.


The Chamber was supposed to be a silver soldered fabrication of 1” square brass tubing and sheet. I didn’t have the tube but did have a piece of 1” brass square bar stock. So the Chamber was machined from solid.


The Chamber was screwed onto the threaded barrel so the bottom could be faced to length.


Here is the start of the gas connector; it is threaded ¼”-32 to screw into the Barrel. I’m using a Jet from a propane torch that has just the right orifice size. Here the connector is being bored for a light press fit for the jet.


The rest of the connector is profiled then parted off.


Flipped around and the barb is finished.


I made the barrel to the print and could not get it to light at any pressure. The two ¼” holes did seem somewhat large. I have built Jerry Howell’s mini propane burners with great success so I dug out his plans and incorporated some of his design into my burner. First the plans call for a straight through bore in the barrel. Jerry’s burner uses a venturi; it also uses 4ea 3/32” holes for air. Because of the design I decided that it would be easier to machine the venturi as a separate piece. The picture shows a cutaway model of this part.


To machine the inlet profile a D-bit was made with the proper radius.


Here is the finished cutter that worked great. The long exit taper was done with a small solid carbide boring bar.


Here is a family shot of the burner, after some initial tests I decided to also incorporate a shutter to adjust the air intake. Across the bottom from left to right are; Barrel, Shutter, Venturi, Gas Connector with pressed in jet.


Here are a couple shots of the assembly.


And from the bottom.


Here is a fuzzy hand held shot with the lights off. It burns real nice on a couple psi of gas pressure. I have a regulator with a gage; Jerry designed his burner to run at 12 to 15 psi.


It is interesting how the flame acts at different air flows. Of course with the air shut off it is a large soft yellow flame. When you start to add air the flame goes blue and uniform across the ceramic. The with the addition of just a little more air the flame drops down into the depressions as shown in the photo.


Continuing to add more air the ceramic starts to glow orange.


With the air shutter full open the flame is orange and almost invisible; the ceramic is pretty much full orange. I don’t understand what all is going on here but I do find it interesting.

Thanks for stopping by,
Dave

[Kim]

The burner looks like its working great, Dave!  And those burner shots are really fascinating!  It would be interesting to know which is the most efficient flame - the low blue flames or the ones where it recedes and the ceramic turns orange!  Wonder if one would cause faster wear on your ceramic?

Very cool nevertheless!  Great work!
Kim

[Roger B]

Excellent progress   That's an elegant engine 

[Dave Otto]

Thanks Guys,
Yes Kim I would like to know too which flame would be the best; I guess maybe I will find out.
The flame that turns the ceramic bright orange seems to put a lot of heat into the metal parts. I think the blue flame that doesn't turn the ceramic orange may have plenty of heat to run the engine and not heat the furnace bottom up so much?

Dave

[Jasonb]

Have a look through Ramon's Wide A Wake thread as there was some talk of flame patterns there, I think the blue base is best as the orange lacks enough air for efficient combustion, bit less sooty too.

A couple of these engines came up while I was looking for something else, are you going to make one of the small matching turntables to go with it? would be nice for displaying another model if you could have it slowly rotating.

[Zephyrin]

interesting experiments !
I would say that the radiant burner, glowing orange, will be more efficient than the blue flames...as more heat is transmitted by radiation than by conduction and convection, but I wait for experimental results !

[Dave Otto]

Thanks for the comments guys, always appreciated.

Jason, yes my plan is also make the turntable; if you look at the beginning of the thread there is a photo of the castings.
Thanks for the tip on Tug’s thread, lots of good information there and it appears that my burner is functioning quite well. This engine should require very little heat to run so I don’t need a flame thrower. The orange flame and orange ceramic is with the air hole wide open so it is burning clean!

OK, next up is to finish the furnace. This involves some sheet metal and insulation work.

To start with I created a flat pattern and punched out a blank at work, you will see that the finish on this one looks different than the rest of the photos. This was my first pass at it and I had sanded the blank with an orbital sander. I decided to use thinner material as this one was to the print and much too thick. I also put in an offset bend, probably not original but what the heck.
David Abbot had made his furnace shell from SS and silver soldered the joint. The original engine used thin steel more like stove pipe with a single tinner’s rivet to hold it together; so this is what I decided to do.


Some slices of Ren-Shape where epoxied together and turned to make a plug. A ½” hole was reamed in each end to be used for fixturing later.


A relief was machined to accommodate the offset bend in the sheet metal.


The first order of business was to massage a curve in each end of the blank. This is take care of the area that the slip roll can’t get to.


The other end with the offset is worked on.


Here is the blank ready for rolling. My plan was originally to leave the center pieces in place to help with the rolling process but the tabs I had used proved to be too fragile, so I ended up removing them first.


Let the rolling begin, I purchased this little slip roll from Grizzly tool when I was working on my Pacific; it works pretty well and for the price I can’t complain.


The rolling has been finished and the furnace shell is starting to look more like a finished part.


The part has been clamped to the plug using some soft mechanics wire (re-bar tie wire).


Before clamping the part to the plug I laid out the position of the rivet. Here I’m using the laser pointer to center up on the cross hairs. The part has been centered on the ½” pin so it is just a matter of rolling the part on the axis and adjusting in Y to set the position.


The hole is drilled and a temporary rivet installed.


Next I need to find the center of the small hole. This will be used as my datum to machine the large holes. The part is shifted left and right and adjustment made by rolling the plug on the pins until equal reading are achieved when the beam contacts the edge of the hole.


Once the center is located, a 3/16” hole is drilled and reamed for a drill blank.


Now the part is rotated 90 degrees and the drill blank indicated level. The large holes were left undersized so they could be accurately placed at this stage. The hole center was located a specific distance from the top edge and on center line so the transfer tube will fit properly.


The first side was machined then the part rotated 180 dialed in and the second one machined. I could have punched these to size but getting them to be exactly 180 after rolling to size would have taken several iterations, so I chose to do it this way.


I have decided to add some insulation to the furnace which is not part of the plans but did exist in some form on the original engines.
Here I’m tapping holes for some standoffs that will hold the upper insulation heat shield/retainer. I have never seen the how the originals were done but in photos there is evidence of copper fasteners in this area that have been ground off and blended to match the casting.
The UPT is also a diversion that I have been playing with. It is quite addictive and fun to keep adding parts to.


I had some semi rigid insulation that I had left over from another project; a piece of that was carved into shape. The heat shield/retainer plate was punched from .05” galvannealed sheet.
Also seen in this photo are the two standoffs that were added to secure all this.


Here is everything assembled, I had forgot to put in the clearance holes for the furnace screws; so they have been added here.


Here is a view from the top, you can see that the standoffs have been peened and dressed down so they don’t show. There will also be insulation around the inside of the furnace sheet metal and on the bottom. Hopefully this will help keep the heat where it belongs.


A pair of 10-32 x 4” long round head screws were machined to hold it all together; another small deviation from the prints but more true to the original.


Here is the assembled furnace viewed from the front.


And one from the rear.

Thanks for checking in and sorry for the long winded post.

Dave